I dont know if it´s possible to synthesize a Chain effect on Sytrus (FM Synthesizer) can anybody give me a Hint on how to do so ?
Well FM is a good way to go. I would start with a couple sine operators and look for a bell or chime like sound. There should be an inharmonic relationship between the two frequencies.
Once you've got a bell sound, that can be the "clink" of each chain link. You'll have to play with envelopes to make it really clink. They should all be almost but not quite the same frequency/pitch. If you can play a bunch at a time with slightly different pitches that should help you get the sound.
The heavier the chain and the larger the links, the lower the pitch of each "clink" should be. You may or may not want to add a touch of a noise source to the clinks.
That should mostly take care of the chain itself, but you'll want to make thumps and things when the chain hits other surfaces. Like if someone lets the chain fall to the floor, there will be a series of tiny thumps.
Remember, our brains help us hear what we expect to hear, so if it feels close but not quite, you might actually have it. Find or make a video of chains being manipulated and see if you can match that and if matching it makes the sound more convincing. Audiences generally don't try to poke holes in something and ruin their own enjoyment, unless something has already ruined it. Expect them to generally meet you part way.